Diseases of the cardiovascular system affect millions of people each year and are a leading cause of death in the United States and throughout the world. The costs to society from such diseases is enormous both in terms of the lives lost and in terms of the cost of treating patients through surgery. A particularly prevalent form of cardiovascular disease is a reduction in the blood supply leading to the heart caused by atherosclerosis or other condition that creates a restriction in blood flow at a critical point in the cardiovascular system that supplies blood to the heart. In many cases, such a blockage or restriction in the blood flow leading to the heart can be treated by a surgical procedure known as a Coronary Artery Bypass Graft (CABG) procedure, which is more commonly known as a xe2x80x9cheart bypassxe2x80x9d operation. In the CABG procedure, the surgeon removes a portion of a vein from another part of the body to use as a graft and installs the graft at points which bypass the obstruction to restore normal blood flow to the heart.
Although the CABG procedure has become relatively common, the procedure itself is lengthy and traumatic and can damage the heart and cardiovascular system, the central nervous system, and the blood supply itself. In a conventional CABG procedure, the surgeon must make a long incision down the center of the chest, cut through the entire length of the sternum, perform several other procedures necessary to attach the patient to a heart-lung bypass machine, cut off the blood flow to the heart, and then stop the heart from beating in order to install the graft. The lengthy surgical procedures are necessary, in part, to connect the patient to a cardiopulmonary bypass machine to continue the circulation of oxygenated blood to the rest of the body while the bypass graft is sewn into place.
Although several efforts have been made to make the CABG procedure less invasive and less traumatic, most techniques still require cardiac bypass and cardioplegia (stoppage of the heart). The safety and efficacy of CABG procedure could be improved if the surgeon could avoid the need to stop the heart from beating during the procedure, thereby eliminating cardiopulmonary bypass and the lengthy and traumatic surgical procedures necessary to connect the patient to a cardiopulmonary bypass machine to sustain the patient""s life during the procedure. In recent years, a small number of surgeons have begun performing CABG procedures using surgical techniques especially developed so that the CABG procedure could be performed while the heart is still beating. In such procedures, there is no need for any form of cardiopulmonary bypass, no need to perform the extensive surgical procedures necessary to connect the patient to a cardiopulmonary bypass machine, and no need to stop the heart. As a result, the surgery is much less invasive and the entire procedure can typically be achieved through one or two comparatively small incisions in the chest.
Despite the advantages, the beating-heart CABG procedure is not widely practiced, in part, because of the difficulty in performing the necessary surgical procedures using conventional instruments. If special designed instruments were available so that the CABG procedure could be performed on the beating heart, the beating-heart CABG procedure would be more widely practiced and the treatment of cardiovascular disease in a significant patient population would be improved.
As noted above, the CABG procedure requires that a connection for the flow of blood be established between two points to xe2x80x9cbypassxe2x80x9d a diseased area and to restore blood flow to the heart. This procedure is known as an xe2x80x9canastomosis.xe2x80x9d Typically, one end of the by-pass graft is sewn to a source artery with an unobstructed blood flow, such as the left internal mammary artery (LIMA), while the other end of the graft is sewn to a target coronary artery, such as the left anterior descending (LAD) artery, that provides blood flow to the main muscles of the heart. Because the beating-heart CABG procedure is performed while the heart muscle is continuing to contract and pump blood, the anastomosis is difficult to perform because the heart continues to move and to attempt to pump blood while the surgeon is sewing the graft in place. The surgical procedure necessary to install the graft in the beating-heart CABG procedure requires placing a series of sutures through several extremely small vessels that continue to move during the procedure. Moreover, the sutures must be carefully placed so that the graft is firmly attached and does not leak when blood flow through the graft is established. It is also important that the procedure be performed rapidly because the blood flow through the target coronary artery is interrupted or reduced during the procedure to allow the graft to be installed without excessive blood loss. Also, the working space and visual access are limited because the surgeon may be working through a small incision in the chest or may be viewing the procedure on a video monitor if the site of the surgery is viewed via a surgical scope.
A current practice is for the surgeon to place sutures through the heart tissue and, by exerting opposing tension on the sutures, stretch the tissue surrounding the anastomosis to partially reduce the motion of the heart while the graft is installed. This approach is far from ideal. Alternatively, a suction device may be attached to the surface of the heart to fix the motion of the outer layer of surface tissue. In such cases, a suction device typically has several ports incorporated into an instrument may be attached to the heart to apply a negative pressure to the surface tissue. The negative pressure essentially attaches the surface tissue to the apparatus thereby fixing the position of a portion of the surface of the heart. Such devices are described in co-pending application Ser. No. 08/603,328 and U.S. Pat. No. 5,727,569.
While the negative pressure approach may be effective in fixing a portion of the surface tissue of the heart, the negative pressure applied to cardiac tissue can result in temporary hematomas at the site where the suction ports attach to the tissue. Also, the exterior cardiac tissue is fixed in a configuration defined by the shape of the instrument and the orientation of the suction ports. While the heart continues to beat, the heart muscles are contracting to pump blood, which results in the muscles exerting a force directed away from the exterior tissue fixed by suction.
The beating-heart CABG procedure could be greatly improved if the heart could be stabilized during the procedure such that the motion of the heart, particularly at the site of the anastomosis, is minimized even though the heart continues to beat. If effective means for stabilizing the beating heart were available, the beating heart CABG procedure could be performed more easily, more rapidly, more safely, and with less trauma to the patient.
The advantages provided to a surgeon by the instruments and techniques of the invention allow the beating heart CABG procedure to be performed more rapidly with less trauma to the patient, and without CPB or cardioplegia. This invention provides an alternative approach to the suction apparatus by providing devices and methods for stabilizing the motion of the heart using mechanical instruments specially designed to apply a stabilizing force to the heart to minimize the motion of the beating heart during a surgical procedure. The invention enables a surgeon to readily and rapidly perform a beating-heart CABG procedure without the need for cardioplegia or cardiopulmonary bypass. In particular, the methods and devices described here enable the surgeon to stabilize the heart such that an anastomosis can be more readily accomplished by enabling the surgeon to attach the graft to a target coronary artery whose motion is minimized for the duration of the surgical procedure.
Pursuant to the invention, a stabilizing device is introduced through a suitable opening in the chest to provide access to the beating heart. By contacting the heart with the stabilizing means of this invention and by exerting a stabilizing force on the heart, the motion of the heart caused by the contraction of the heart muscles is effectively eliminated such that movement of the target artery at the site of the surgery is minimized. The remainder of the heart may be allowed to contract normally or may have additional devices in place to support the heart or to restrain its motion. An important advantage of this invention is derived from the discovery that an effective procedure can be followed using the devices of the inventors to provide an advantageous technique for stabilizing the beating heart. The procedure requires exerting a stabilizing force on the beating heart using devices constructed as described herein. Typically, in separate steps, the surgeon contacts the heart with the stabilizing means, assesses the degree of movement at the site of the surgery and positions the stabilizing means proximate to the target coronary artery. With the stabilizing means in place, the surgeon applies a stabilizing force to the stabilizing means by applying a force such that the portion of the instrument in contact with the surface of the heart displaces the surface of the heart a sufficient distance that the contraction of the heart does not cause either vertical or horizontal motion at the surgery site. The stabilizing force is applied by the stabilizing means of the invention and comprised of exerting a mechanical force onto the beating heart at the location of the target coronary artery. Thus, an important aspect of this invention is the discovery that the beating heart may be effectively stabilized for the purpose of a surgical procedure by using a specially designed instrument as described herein to exert a mechanical stabilizing force on the exterior of the heart proximate to the site of the surgery.
By fixing the position of the stabilizing means in a configuration where the motion of the beating heart is effectively eliminated, the surgeon maintains the stabilizing force on the beating heart for the duration of the procedure. To fix the position of the stabilizing means, the means may be attached to a retractor used to separate the ribs or to another fixed support. Alternatively, the stabilizing means may be attached to a semi-rigid conformable arm which is rendered rigid by mechanically, chemically, or by human intervention. In certain preferred embodiments, the stabilizing means has an adjustable shaft means which may be oriented in several directions and has a fixture adapted to be attached to a retractor. In a preferred technique of the invention, the surgeon first performs a thoracotomy, retracts the ribs using a retractor which is locked in an open position providing access to the beating heart. The surgeon then contacts the surface of the heart with the stabilizing means at a point proximate to the target coronary artery, and exerts a stabilizing force on the stabilizing means until the site of the surgery is substantially motionless. At this point, the adjustable shaft means is positioned and fixed in place by attachment to the retractor thereby rendering the target coronary artery substantially motionless for the duration of the procedure.